Resin film, copper foil with resin, multilayered wiring board, coil structure, and magnetic device

Abstract

A resin film (100) comprises a core layer (2) and adhesive resin layers (1) provided respectively to both surfaces of the core layer (2), wherein the adhesive resin layers (1) are made of a first adhesive resin composition, which includes a poly(amic acid) that is a product of polyaddition reaction between an acid dianhydride (A) and a diamine (B), or a second adhesive resin composition, which includes an epoxy resin. In the first adhesive resin composition, the poly(amic acid) includes a dimer diamine (B1) at a molar ratio of 0.2 or higher with respect to the whole diamine component. A cured object formed from the second adhesive resin composition has a dielectric breakdown strength of 300 kV / mm or greater. The core layer (2) is a polyimide film comprising a polyimide obtained by imidizing the poly(amic acid) contained in the first adhesive resin composition.

Description

Resin film, copper foil with resin, multilayer wiring board, coil structure, and magnetic device

[0001] The present invention relates to a resin film, a copper foil with resin, a multilayer wiring board, a coil structure, and a magnetic device.

[0002] As a thin transformer, which is one of magnetic devices, for example, Patent Document 1 describes a thin transformer including a printed coil and a core made of a magnetic material, and a terminal base on which the printed coil and the core are mounted. This thin transformer is characterized in that the surface where the conductor of the printed coil is exposed is covered with a heat-resistant resin.

[0003] Japanese Patent Application Laid-Open No. 9-326316

[0004] However, in recent years, magnetic devices have been required to handle higher voltages and larger currents. When using a conventional prepreg (glass cloth base / epoxy resin) as the heat-resistant resin layer, it has not been possible to satisfy both sufficient thinness and sufficient withstand voltage. Furthermore, the conventional prepreg has a problem of high dielectric constant.

[0005] An object of the present invention is to provide a resin film with a low dielectric constant, and a copper foil with resin, a multilayer wiring board, a coil structure, and a magnetic device using the same.

[0006] The present invention provides the following resin film, resin-coated copper foil, multilayer wiring board, coil structure, and magnetic device. [1] A resin film comprising a core layer and adhesive resin layers provided on both sides of the core layer, wherein the adhesive resin layer is made of a first adhesive resin composition containing polyamic acid which is a polyaddition reaction product of (A) an acid dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin, wherein the polyamic acid in the first adhesive resin composition contains (B1) dimeramine in a molar ratio of 0.2 or more with respect to the total diamine components, the dielectric breakdown strength of the cured product of the second adhesive resin composition is 300 kV / mm or more, and the core layer is made of a polyimide film containing a polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. [2] A resin film according to [1], wherein the (A) acid dianhydride has a structure represented by the following formula (1).

[0007]

[0008] (In formula (1), Ar represents a substituted or unsubstituted arylene group.) [3] A resin film according to [1] or [2], wherein the (B) diamine comprises an (B2) aromatic diamine. [4] A resin film according to any one of [1] to [3], wherein the ratio of the thickness of the adhesive resin layer to the thickness of the core layer is 1 / 2 or more and 4 or less. [5] A resin-coated copper foil comprising a resin film according to any one of [1] to [4] and a copper foil laminated on the resin film. [6] A multilayer wiring board comprising an insulating layer formed using a resin film according to any one of [1] to [4]. [7] A coil structure comprising an insulating layer formed using a resin film according to any one of [1] to [4]. [8] A magnetic device comprising an insulating layer formed using a resin film according to any one of [1] to [4].

[0009] According to one aspect of the present invention, a resin film with a low dielectric constant, as well as a resin-coated copper foil, a multilayer wiring substrate, a coil structure, and a magnetic device using the same, can be provided.

[0010] This is a schematic diagram showing a resin film according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a resin film according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a resin film according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a resin film according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing resin-coated copper foil according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing resin-coated copper foil according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the first embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the second embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the second embodiment of the present invention. This is an explanatory diagram showing an example of a method for manufacturing a multilayer wiring board according to the third fourth embodiment of the present invention. This is a cross-sectional view showing the VIII-VIII section of Figure 7.

[0011] [First Embodiment] The present invention will be described below with reference to embodiments, based on the drawings. The present invention is not limited to the contents of the embodiments. Note that in the drawings, some parts have been enlarged or reduced in size for the purpose of facilitating the explanation.

[0012] (Resin Film) As shown in Figure 1, the resin film 100 according to this embodiment comprises a core layer 2, an adhesive resin layer 1, and a release film layer 3. The adhesive resin layer 1 is provided on both sides of the core layer 2. The release film layer 3 is provided on top of the adhesive resin layer 1. When using the resin film 100, the release film layer 3 is peeled off from the adhesive resin layer 1 before use. The adhesive resin layer 1 consists of a first adhesive resin composition containing polyamic acid, which is a polyaddition reaction product of (A) an acid dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin. The polyamic acid in the first adhesive resin composition must contain (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. The dielectric breakdown strength of the cured product of the second adhesive resin composition must be 300 kV / mm or more. Furthermore, the core layer 2 must consist of a polyimide film containing polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. The reason why the resin film 100 according to this embodiment has a low dielectric constant is as follows. Specifically, the resin film 100 has a core layer 2 made of a polyimide film containing a polyimide obtained by imidizing polyamic acid in the first adhesive resin composition, which has a low dielectric constant. Furthermore, the dielectric constant of the cured product of the adhesive resin layer 1 is low. In addition, the adhesive resin layer 1 contains epoxy resin or a polyamic acid solution and has sufficient adhesive properties, so a multilayer wiring board 300 (see Figures 4A to 4D) can be manufactured using this resin film 100.

[0013] (Adhesive resin layer) The adhesive resin layer 1 is a layer made of a first adhesive resin composition or a second adhesive resin composition.

[0014] (First Adhesive Resin Composition) The first adhesive resin composition used in this embodiment is an adhesive resin composition containing polyamic acid, which is a polyaddition reaction product of (A) an acidic dianhydride and (B) a diamine. The polyamic acid in this first adhesive resin composition must contain (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. That is, the polyimide formed using the polyamic acid used in this embodiment has an ester skeleton and a dimer skeleton, and low water absorption can be achieved due to the ester skeleton. Furthermore, low dielectric properties are exhibited due to the dimer skeleton, and by including a certain amount of dimeramine as a diamine component, the dielectric constant and dielectric loss tangent can be further reduced, thereby achieving the desired low dielectric properties. In addition, the presence of a dimer skeleton in the polyimide improves heat resistance, and a polyimide with excellent heat decomposition resistance can be formed.

[0015] (Component (A)) The polyamic acid used in this embodiment uses (A) an acid dianhydride as one of its raw materials. Any known acid dianhydride can be used as appropriate. Examples of acid dianhydride components include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride, and ester-type acid dianhydrides having ester bonds in the molecule. In this embodiment, it is preferable that the acid dianhydride component has structural units derived from ester-type acid dianhydrides having ester bonds in the molecule. By having structural units derived from ester-type acid dianhydrides in the polyamic acid, low water absorption can be imparted to the resulting polyimide. The acid dianhydride has two acid anhydride groups in one molecule, and is preferably a tetracarboxylic acid dianhydride, and more preferably an aromatic tetracarboxylic acid dianhydride. There may be one or more ester bonds in the molecule, preferably one to three, and more preferably one or two. Acidic dianhydrides may be used individually or in combination of two or more types.

[0016] Such acidic dianhydrides preferably have the structure shown in the following formula (1). In formula (1), Ar represents a substituted or unsubstituted arylene group, and a substituted arylene group means that the hydrogen atoms of an unsubstituted arylene group are substituted with any substituent. The number of carbon atoms in the substituted or unsubstituted arylene group (excluding the number of carbon atoms of the substituent) is preferably 6 or more and 20 or less, and more preferably 6 or more and 12 or less.

[0017]

[0018] In formula (1), examples of unsubstituted arylene groups in Ar include o-phenylene, m-phenylene, p-phenylene, 2,6-naphthylene, and 4,4'-biphenylylene. Among these, p-phenylene, 2,6-naphthylene, or 4,4'-biphenylylene are preferred.

[0019] Examples of substituents on the substituted arylene group include C1-C8 alkyl groups, halogen atoms (fluorine, chlorine, bromine, or iodine atoms), and halogenated alkyl groups in which the hydrogen atoms of the alkyl group are substituted with the halogen atoms. Among these substituents, C1-C8 alkyl groups are preferred, and methyl groups are more preferred. The number of substituents may be one or two or more. If there are two or more substituents, they may be the same or different. Specific examples of substituted arylene groups include the 2,2',3,3',5,5'-hexamethyl-4,4'-biphenylylene group.

[0020] Preferred examples of the acid dianhydride represented by formula (1) include the compound represented by the following formula (1-1) and the compound represented by the following formula (1-2) (TAHQ), with the compound represented by the following formula (1-2) (TMPBP-TME) being more preferred.

[0021]

[0022] (Component (B)) The polyamic acid used in this embodiment uses (B) diamine as one of its raw materials. Any known diamine can be used as appropriate. The diamine component has structural units derived from a diamine, and one of the diamine components has structural units derived from (B1) dimer amine. Here, dimer amine is a cyclic or acyclic dimer acid obtained as a dimer of an unsaturated fatty acid in which two terminal carboxylic acid groups (-COOH) are primary aminomethyl groups (-CH ２ -NH ２ ) or amino group (-NH ２ This refers to an aliphatic diamine substituted with (B1). By having a polyamic acid with structural units derived from dimer amine, low dielectric properties can be imparted to the resulting polyimide. (B1) Dimer amine may be used alone or in combination of two or more types.

[0023] Dimer acids are dibasic acids obtained by the intermolecular polymerization reaction of unsaturated fatty acids. Aliphatic diamines derived from dimer acids are obtained by polymerizing unsaturated fatty acids such as oleic acid, linoleic acid, or linolenic acid to form dimer acids, which are then reduced and aminated. Such dimer amines are preferably diamine compounds obtained by substituting the terminal carboxylic acid group of a dibasic acid compound having 18 to 54 carbon atoms, preferably 22 to 44 carbon atoms, with a primary aminomethyl group or an amino group.

[0024] Commercially available dimeramines include "Versamin® 551" and "Versamin® 552" from Cognics Japan, and "PRIAMINE® 1073," "PRIAMINE® 1074," and "PRIAMINE® 1075" from Croda Japan.

[0025] Furthermore, the polyamic acid used in this embodiment contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components. By including dimeramine in a specific molar ratio or higher relative to the total diamine, the resulting polyimide can be given a lower dielectric constant and a lower dielectric loss tangent. The molar ratio of (B1) dimeramine to the total diamine components is preferably 0.3 or higher, and more preferably 0.4 or higher.

[0026] The polyamic acid used in this embodiment preferably contains a (B2) aromatic diamine as another diamine component. Examples of (B2) aromatic diamines include p-phenylenediamine (PDA), m-phenylenediamine, 4,4'-oxydianiline (ODA), 3,3'-bistrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis(anilino)ethane, diaminodiphenylsulfone, Examples include diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis(p-aminophenyl)propane, 2,2-bis(p-aminophenyl)hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis(p-aminophenoxy)benzene, 4,4'-bis(p-aminophenoxy)biphenyl, diaminoanthraquinone, and 4,4'-bis(3-aminophenoxyphenyl)diphenylsulfone. Among these aromatic diamines, PDA, ODA, or TFMB are preferred, with ODA being more preferred. (B2) Aromatic diamines may be used alone or in combination of two or more.

[0027] The molar ratio of diamine to acidic dianhydride [(B) / (A)] is not particularly limited, but is preferably 0.90 or more and 1.10 or less, more preferably 0.95 or more and 1.05 or less, even more preferably 0.97 or more and 1.03 or less, and particularly preferably 0.98 or more and 1.02 or less.

[0028] (Component (C)) The polyamic acid used in this embodiment can be synthesized by known general methods. For example, a polyamic acid composition (polyamic acid solution) can be obtained by reacting (A) an acidic dianhydride and (B) a diamine in (C) an organic solvent. The organic solvent used for polymerization of polyamic acid is not particularly limited as long as it can dissolve the acidic dianhydride and diamine as monomer components and also dissolve the polyamic acid produced by the polyaddition reaction. Examples of such organic solvents include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphate triamide; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform and methylene chloride; aromatic hydrocarbon-based solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. These organic solvents may be used individually or in combination of two or more. From the viewpoint of enhancing the solubility and reactivity of polyamic acids, the organic solvent is preferably selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, with amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, and N-methyl-2-pyrrolidone being more preferred.

[0029] The molecular weight of polyamic acid can be adjusted by adjusting the molar ratio of the total number of moles of the acid dianhydride component to the total number of moles of the diamine component. The molecular weight (weight-average molecular weight) of polyamic acid is not particularly limited, but from the viewpoint of solubility in organic solvents, it is more preferable to be between 10,000 and 100,000. The weight-average molecular weight of polyamic acid can be determined, for example, from the value converted to standard polystyrene by gel filtration chromatography (GPC) measurement.

[0030] The synthesis of polyamic acids by the polyaddition reaction of acidic dianhydrides and diamines is preferably carried out in an inert atmosphere such as argon or nitrogen. In an inert atmosphere, the polyaddition reaction proceeds by dissolving the acidic dianhydride and diamine in an organic solvent and mixing them. The order of addition of the acidic dianhydride and diamine is not particularly limited. For example, the diamine may be dissolved in an organic solvent or dispersed in a slurry to form a diamine solution, and the acidic dianhydride may be added to the diamine solution. The acidic dianhydride and diamine may be added directly to the organic solvent in a solid state, or they may be added separately dissolved in an organic solvent or dispersed in a slurry.

[0031] The temperature conditions for the polyaddition reaction are not particularly limited, but from the viewpoint of suppressing the decrease in molecular weight of the polyamic acid due to depolymerization, the reaction temperature is preferably 100°C or lower, and from the viewpoint of allowing the polyaddition reaction to proceed appropriately, the reaction temperature is more preferably 20°C to 80°C. The reaction time can be arbitrarily set in the range of 1 hour to 72 hours, and if necessary, it may be left overnight at room temperature.

[0032] When preparing the polyamic acid composition used in this embodiment, the viscosity of the solution is preferably 500 mPa·s or higher from the viewpoint of film-forming properties. Furthermore, the concentration of polyamic acid in the polyamic acid composition used in this embodiment is preferably 10% by mass or higher, more preferably 15% by mass or higher, and even more preferably 25% by mass or higher. In particular, if the concentration of polyamic acid is 15% by mass or higher, the productivity when forming a polyimide coating film using polyamic acid can be increased. Furthermore, the upper limit of the concentration of polyamic acid is preferably 50% by mass or lower, and even more preferably 30% by mass or lower, from the viewpoint of sufficiently dissolving the polyamic acid in the organic solvent.

[0033] To impart processing properties or various functionalities to polyamic acid and polyimides formed using said polyamic acid, various organic or inorganic low-molecular-weight or high-molecular-weight compounds may be blended into the polyamic acid composition. For example, the polyamic acid composition may contain solvent-soluble polyimide resin, flame retardants, dyes, surfactants, leveling agents, plasticizers, fine particles, sensitizers, or silane coupling agents. The fine particles may be either organic or inorganic, and may have a porous or hollow structure. Furthermore, after polyimidization of the polyamic acid, some of the amino groups may be maleimidized.

[0034] (Second Adhesive Resin Composition) The second adhesive resin composition used in this embodiment is an adhesive resin composition containing epoxy resin. The dielectric breakdown strength of the cured product of this second adhesive resin composition must be 300 kV / mm or higher. If this dielectric breakdown strength is below the lower limit, the dielectric strength of the resin film 100 will be insufficient, and it will be difficult to make it thin because it will be necessary to ensure a sufficient film thickness for dielectric strength. From a similar viewpoint, the dielectric breakdown strength of the cured product of the adhesive resin composition is preferably 320 kV / mm or higher, and more preferably 340 kV / mm or higher. The adhesive resin layer 1 may be formed by applying a coating liquid for the second adhesive resin composition and drying it. Alternatively, the second adhesive resin composition may be B-staged by heat. The coating liquid for the second adhesive resin composition must contain epoxy resin, and preferably contains epoxy resin, an aromatic amine-based curing agent, and a solvent-soluble polyimide resin. By B-staged this second adhesive resin composition, an adhesive resin layer 1 with sufficient fluidity and adhesion can be obtained. Furthermore, the coating liquid for the second adhesive resin composition may contain fillers, curing accelerators, flame retardants, and solvents as needed.

[0035] Any epoxy resin having two or more glycidyl groups can be used. Suitable epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolacphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, and dicyclopentadiene type epoxy resin. These may be used individually or in combination of two or more types.

[0036] Aromatic amine curing agents are not particularly limited as long as they have an aromatic group and an amino group and have the effect of accelerating the curing of epoxy resins when irradiated with light. Examples of aromatic groups include phenyl groups, biphenyl groups, and fluorenyl groups. Examples of aromatic amine curing agents include polytetramethylene oxide-di-p-aminobenzoate, 4,4'-diaminodiphenylsulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, trimethylenebis( Examples include 4-aminobenzoate, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfone, 9,9'-bis(4-aminophenyl)fluorene, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. These may be used individually or in combination of two or more.

[0037] When the number of moles of epoxy resin is set to 1, the amount of aromatic amine-based curing agent used is preferably 0.2 moles or more and 1.5 moles or less. If the amount used is above the lower limit, it tends to be easier to obtain appropriate toughness and chemical resistance. On the other hand, if the amount used is below the upper limit, it tends to be easier to obtain appropriate Tg and thermal expansion coefficient.

[0038] The solvent-soluble polyimide resin is a polyimide resin that is soluble in the solvent used in the production of the second adhesive resin composition used in this embodiment. Preferred solvent-soluble polyimide resins have high Tg, low thermal expansion coefficient, excellent film properties, low dielectric constant, and low dielectric loss tangent. Examples of solvent-soluble polyimide resins include fully imidized soluble polyimide resins obtained by reacting diaminotrimethylphenylindan with benzophenonetetracarboxylic acid 2-anhydride. This compound can improve adhesive strength without the need for other adhesion-imparting agents. The number-average molecular weight (Mn) of the solvent-soluble polyimide resin is not particularly limited, but is preferably between 10,000 and 50,000, and particularly preferably between 12,000 and 20,000.

[0039] When the total amount of epoxy resin and aromatic amine-based curing agent is 100 parts by mass, the amount of solvent-soluble polyimide resin blended is preferably 10 parts by mass or more and 100 parts by mass or less, and particularly preferably 15 parts by mass or more and 100 parts by mass or less. If the blending amount is above the lower limit, it tends to be easier to obtain an improvement in adhesive strength and flexibility. If the blending amount is below the upper limit, it tends to be easier to ensure the breaking strength of the film.

[0040] Examples of fillers include silica, alumina, aluminum hydroxide, and magnesium hydroxide. These may be used individually or in combination of two or more. Examples of curing accelerators include imidazoles. These may be used individually or in combination of two or more. Examples of flame retardants include condensed phosphate esters, phosphazenes, polyphosphates, and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivatives. These may be used individually or in combination of two or more. Examples of solvents include NMP (N-methylpyrrolidone), diethylene glycol monomethyl ether acetate, cyclohexanone, and MEK (methyl ethyl ketone). These may be used individually or in combination of two or more.

[0041] The thickness of the adhesive resin layer 1 varies according to the copper thickness of the wiring board to be joined and is not particularly limited. For example, when the copper thickness of the wiring board is 25 μm, the thickness of the adhesive resin layer 1 is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, still more preferably 15 μm or more and 50 μm or less, and particularly preferably 20 μm or more and 30 μm or less. If the thickness is below the upper limit, the thickness of the resin film 100 can be made thinner. If the thickness is above the lower limit, the adhesiveness of the resin film 100 can be improved.

[0042] (Core layer) The core layer 2 needs to be a layer made of a polyimide film containing polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition. The method for converting polyamic acid to polyimide is not particularly limited, but polyimide can be produced by dehydrating and cyclizing (imidizing) the polyamic acid obtained as described above. As the method for dehydrating and cyclizing (imidizing), known methods such as thermal imidization by heating to dehydrate and cyclize or chemical imidization by chemically cyclizing using a known dehydrating and cyclizing catalyst can be employed.

[0043] In the case of thermal imidization, the heating temperature is preferably 120°C or more and 350°C or less, more preferably 150°C or more and 250°C or less. The heating time is preferably 3 minutes or more and 3 hours or less, more preferably 5 minutes or more and 2 hours or less. In the case of chemical imidization, as the dehydrating and cyclizing catalyst, for example, pyridine, triethylamine, or acetic anhydride can be used. At this time, the reaction temperature can be any temperature selected from 20°C or more and 180°C or less, but is preferably 150°C or less. Also, the reaction time is preferably 1 hour or more and 3 hours or less. The imidization can be carried out under air, reduced pressure, or in an inert gas such as nitrogen, but in order to obtain a polyimide film with high transparency, it is preferably carried out under reduced pressure or in an inert gas such as nitrogen.

[0044] The molecular weight (weight-average molecular weight) of the polyimide is not particularly limited, but from the viewpoints of the low dielectric constant characteristics, solubility in organic solvents, or film-forming properties of the obtained polyimide, it is preferably 10,000 or more and 100,000 or less. The weight-average molecular weight of the polyimide can be determined, for example, from the standard polystyrene conversion value by gel permeation chromatography (GPC) measurement.

[0045] The polyimide film used in this embodiment contains the polyimide obtained as described above. The method for producing such a polyimide film is not particularly limited. For example, the above-mentioned polyamic acid composition is applied in a film form on a substrate (for example, a plastic film made of a resin such as polyethylene, polypropylene, urethane, polyester, polyethylene terephthalate (PET), or polycarbonate, a glass plate, a stainless steel plate, a copper plate including a thin copper foil, or an aluminum plate, etc.), and then dried and heated to remove the solvent and dehydrate and close the ring (imidization), or a method of dissolving the polyimide obtained by converting the polyamic acid into a polyimide in an organic solvent, applying the polyimide solution in a film form on the substrate, and drying and removing the solvent, etc. can be mentioned. The method for applying to the substrate is not particularly limited, and a conventionally known coating method can be applied.

[0046] The thickness of the polyimide film is not particularly limited and can be appropriately selected according to the application. The thickness of the polyimide film can be easily controlled by appropriately adjusting the solid content concentration, coating thickness, viscosity, etc. of each component in the polyamic acid composition. By this core layer 2, the withstand voltage of the resin film 100 can be improved and the dielectric constant can be lowered. Furthermore, since this core layer 2 can maintain the withstand voltage even when it is made thin, the resin film 100 can be made thinner.

[0047] The thickness of the core layer 2 varies depending on the configuration of the wiring board to be bonded, and is not particularly limited. For example, the thickness of the core layer 2 is preferably 5 μm to 100 μm, more preferably 7 μm to 50 μm, and particularly preferably 10 μm to 30 μm. If the thickness is below the upper limit, the thickness of the resin film 100 can be made thinner. If the thickness is above the lower limit, the insulating properties of the resin film 100 can be improved.

[0048] From the viewpoint of balancing various physical properties of the resin film 100, such as dielectric strength, dielectric constant, and adhesiveness, the ratio of the thickness of the adhesive resin layer 1 to the thickness of the core layer 2 (thickness of adhesive resin layer 1 / thickness of core layer 2) is preferably 1 / 2 or more and 4 or less, more preferably 2 / 3 or more and 4 or less, even more preferably 1 or more and 3 or less, and particularly preferably 3 / 2 or more and 5 / 2 or less.

[0049] (Release Film Layer) The release film layer 3 is a layer made of release film provided on the adhesive resin layer 1. When using the resin film 100, the release film layer 3 can be peeled off from the adhesive resin layer 1 and used. Alternatively, the release film layer 3 can be coated with a coating liquid for the adhesive resin composition to form a film and create a B-stage, making it easy to form the adhesive resin layer 1. The release film layer 3 is not necessarily required. The release film layer 3 is a component that is provided as needed. Examples of release films include polyethylene terephthalate film (PET film) and polyethylene naphthalate film. The surface of the release film may be treated with a release agent.

[0050] (Method for Manufacturing Resin Film) The method for manufacturing the resin film 100 according to this embodiment is not particularly limited. The resin film 100 can be manufactured, for example, as shown in Figures 2A to 2C, by a method comprising: a film-forming step of applying a coating liquid for an adhesive resin composition (a coating liquid containing either the first adhesive resin composition or the second adhesive resin composition described above) onto a release film layer 3 to form a coated film 1b; a drying step of drying the coated film 1b formed in the film-forming step to form an adhesive resin layer 1 and obtain an adhesive laminated film; and a lamination step of sandwiching a core layer 2 between the two adhesive laminated films obtained in the drying step and laminating them to obtain the resin film 100. In this embodiment, the case in which the second adhesive resin composition is used as the adhesive resin composition will be described as an example.

[0051] In the film formation process, as shown in Figure 2A, a coating liquid for the adhesive resin composition is applied to the release film layer 3 to form a film. Examples of coating devices for the adhesive resin composition include bar coaters, die coaters, curtain coaters, spray coaters, roll coaters, and screen printing machines. The coating thickness of the adhesive resin composition is preferably adjusted so that the thickness of the adhesive resin layer 1 falls within the aforementioned range.

[0052] In the drying process, as shown in Figure 2B, the coated film 1b formed in the film formation process is dried to form an adhesive resin layer 1 and obtain an adhesive laminated film. The drying temperature is preferably 100°C to 160°C, more preferably 105°C to 155°C, and particularly preferably 110°C to 150°C. If the temperature is within this range, the adhesive resin composition can be appropriately B-staged. The drying time is preferably 10 seconds to 600 seconds, more preferably 15 seconds to 500 seconds, and particularly preferably 30 seconds to 500 seconds. If the time is within this range, the adhesive resin composition can be appropriately B-staged.

[0053] In the lamination process, as shown in Figure 2C, the core layer 2 is sandwiched between two adhesive laminated films obtained in the drying process and laminated to obtain a resin film 100. Here, the core layer 2 is sandwiched between the two adhesive laminated films so that the release film layer 3 of the adhesive laminated film is on the outside. Since the adhesive resin layer 1 has adhesive properties, a resin film 100 can be obtained. As for the lamination, vacuum pressure lamination, vacuum roll lamination, and roll lamination can be used. In this way, the resin film 100 according to this embodiment can be manufactured.

[0054] (Copper foil coated with resin) The copper foil coated with resin 200 according to this embodiment comprises the resin film 100 according to this embodiment described above and a copper foil 4 laminated on the resin film 100. The copper foil coated with resin 200 can be manufactured by a method comprising, for example, a release film removal step of removing the release film layer 3 from the resin film 100, as shown in Figures 3A and 3B, and a lamination step of laminating the copper foil 4 onto the resin film 100 from which one of the release film layers 3 has been removed to obtain the copper foil coated with resin 200.

[0055] In the release film removal process, as shown in Figure 3A, one of the release film layers 3 is removed from the resin film 100. The release film layer 3 is for protecting the adhesive resin layer 1 until use, and can be removed by peeling it off the adhesive resin layer 1.

[0056] In the lamination process, as shown in Figure 3B, a copper foil 4 is laminated onto a resin film 100 from which one of the release film layers 3 has been removed to obtain a resin-coated copper foil 200. With one of the release film layers 3 removed, the adhesive resin layer 1 is exposed on the resin film 100. The exposed adhesive resin layer 1 and the matte surface of the copper foil 4 are then placed in contact and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a resin-coated copper foil 200 can be obtained.

[0057] (Multilayer Wiring Board) The multilayer wiring board 300 according to this embodiment includes an insulating layer formed using the resin film 100 according to this embodiment described above. The multilayer wiring board 300 can be manufactured by a method comprising, for example, as shown in Figures 4A to 4D, a release film removal step of removing both release film layers 3 from the resin film 100; a lamination step of sandwiching the resin film 100 from which the release film layers 3 have been removed between two copper foils 4 to obtain a copper-clad laminate; a thermosetting step of applying a thermosetting treatment to the adhesive resin layer 1 of the copper-clad laminate obtained in the lamination step to obtain a copper-clad laminate substrate; and an etching step of etching the copper foils 4 of the copper-clad laminate substrate so that wiring 41 of a predetermined pattern are formed to obtain a multilayer wiring board 300.

[0058] In the release film removal process, both release film layers 3 are removed from the resin film 100, as shown in Figure 4A.

[0059] In the lamination process, as shown in Figure 4B, the resin film 100 from which the release film layer 3 has been removed is sandwiched between two copper foils 4 to obtain a copper-clad laminate. Preferably, one side of the copper foil 4 is a matte surface. Also, preferably, the two copper foils 4 are arranged so that their matte surfaces face each other. Here, the resin film 100 from which the release film layer 3 has been removed is sandwiched between two copper foils 4 and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a copper-clad laminate can be obtained.

[0060] In the thermosetting process, as shown in Figure 4C, the adhesive resin layer 1 of the copper-clad laminate obtained in the lamination process is subjected to a thermosetting treatment to obtain a copper-clad laminate substrate. The adhesive resin layer 1 becomes a cured resin layer 1a consisting of a cured product of the adhesive composition by the thermosetting treatment. Examples of thermosetting treatments include heat-pressing treatment and heat treatment. The thermosetting treatment may be a one-step treatment or a two-step or more treatment. The temperature of the thermosetting treatment is preferably 130°C to 200°C, and particularly preferably 150°C to 190°C. The pressure of the thermosetting treatment is preferably 0.1 MPa to 10 MPa, and particularly preferably 0.5 MPa to 4 MPa. The time of the thermosetting treatment is preferably 0.5 hours to 4 hours, and particularly preferably 1 hour to 3 hours.

[0061] In the etching process, as shown in Figure 4D, the copper foil 4 of the copper-clad laminate is etched so that wiring 41 of a predetermined pattern is formed to obtain a multilayer wiring substrate 300. To form the wiring 41 of a predetermined pattern, for example, an etching resist may be used. Specifically, the wiring 41 of a predetermined pattern can be formed by forming an etching resist pattern on the copper foil 4 and then performing an etching process.

[0062] As described above, the multilayer wiring board 300 according to this embodiment can be manufactured. This multilayer wiring board 300 is a two-layer wiring board having two layers of wiring 41.

[0063] [Second Embodiment] Next, a second embodiment of the present invention will be described based on the drawings. The description of the same configuration as in the first embodiment will be omitted. The multilayer wiring board 300A according to this embodiment is a four-layer wiring board having four layers of wiring 41, as shown in Figure 5C. The multilayer wiring board 300A can be manufactured by a method comprising, for example, preparing two multilayer wiring boards 300 and one resin film 100, a release film removal step of removing the release film layer 3 from the resin film 100, a lamination step of sandwiching the resin film 100 from which the release film layer 3 has been removed between two multilayer wiring boards 300 to obtain a wiring laminate, and a thermosetting step of applying a thermosetting treatment to the adhesive resin layer 1 of the wiring laminate obtained in the lamination step to obtain a multilayer wiring board 300A.

[0064] In the release film removal process, as shown in Figure 5A, two multilayer wiring boards 300 and one resin film 100 are prepared, and the release film layer 3 is removed from the resin film 100.

[0065] In the lamination process, as shown in Figure 5B, the resin film 100 from which the release film layer 3 has been removed is sandwiched between two multilayer wiring boards 300 to obtain a wiring laminate. Here, the resin film 100 from which the release film layer 3 has been removed is sandwiched between two multilayer wiring boards 300 and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a copper-clad laminate can be obtained. It is preferable that the thickness of the adhesive resin layer 1 is greater than the thickness of the wiring 41 of the multilayer wiring board 300. With such a configuration, the wiring 41 can be embedded in the adhesive resin layer 1.

[0066] In the thermosetting process, as shown in Figure 5C, the adhesive resin layer 1 of the wiring laminate obtained in the lamination process is subjected to a thermosetting treatment to obtain a multilayer wiring substrate 300A. The adhesive resin layer 1 becomes a cured resin layer 1a consisting of a cured product of the adhesive composition after the thermosetting treatment. The thermosetting treatment is as described above.

[0067] As described above, the multilayer wiring board 300A according to this embodiment can be manufactured. This multilayer wiring board 300A is a four-layer wiring board having four layers of wiring 41. Furthermore, wiring boards with an even number of layers (six or more) can be manufactured by applying the manufacturing method of the multilayer wiring board 300A according to this embodiment.

[0068] [Third Embodiment] Next, a third embodiment of the present invention will be described based on the drawings. The description of the same configuration as in the first embodiment will be omitted. The multilayer wiring board 300B according to this embodiment is a three-layer wiring board having three layers of wiring 41, as shown in Figure 6D. The multilayer wiring board 300B can be manufactured by a method comprising, for example, preparing one multilayer wiring board 300 and one resin-coated copper foil 200, as shown in Figures 6A to 6D, a release film removal step of removing the release film layer 3 from the resin-coated copper foil 200, a lamination step of laminating the resin-coated copper foil 200 from which the release film layer 3 has been removed onto the multilayer wiring board 300 to obtain a copper foil-coated wiring laminate, a heat curing step of applying a heat curing treatment to the adhesive resin layer 1 of the copper foil-coated wiring laminate obtained in the lamination step to obtain a copper foil-coated wiring laminate, and an etching step of etching the copper foil 4 of the copper foil-coated wiring laminate so that wiring 41 of a predetermined pattern is formed to obtain the multilayer wiring board 300B.

[0069] In the release film removal process, as shown in Figure 6A, one multilayer wiring board 300 and one resin-coated copper foil 200 are prepared, and the release film layer 3 is removed from the resin-coated copper foil 200.

[0070] In the lamination process, as shown in Figure 6B, the resin-coated copper foil 200 from which the release film layer 3 has been removed is laminated onto a multilayer wiring substrate 300 to obtain a copper foil-coated wiring laminate. When the release film layer 3 has been removed from the resin-coated copper foil 200, the adhesive resin layer 1 is exposed. The exposed adhesive resin layer 1 and the multilayer wiring substrate 300 are then positioned in contact and laminated. The lamination is as described above. Since the adhesive resin layer 1 has adhesive properties, a copper foil-coated wiring laminate can be obtained.

[0071] In the thermosetting process, as shown in Figure 6C, the adhesive resin layer 1 of the copper foil-equipped wiring laminate obtained in the lamination process is subjected to a thermosetting treatment to obtain a copper foil-equipped wiring laminate substrate. The adhesive resin layer 1 becomes a cured resin layer 1a consisting of a cured product of the adhesive composition after the thermosetting treatment. The thermosetting treatment is as described above.

[0072] In the etching process, as shown in Figure 6D, the copper foil 4 of the copper foil-equipped wiring laminate is etched so that wiring 41 of a predetermined pattern is formed to obtain a multilayer wiring substrate 300B. The etching is as described above.

[0073] As described above, the multilayer wiring board 300B according to this embodiment can be manufactured. This multilayer wiring board 300B is a three-layer wiring board having three layers of wiring 41. Furthermore, wiring boards with an odd number of layers (five or more) can be manufactured by applying the manufacturing method of the multilayer wiring board 300B according to this embodiment.

[0074] [Fourth Embodiment] Next, a fourth embodiment of the present invention will be described based on the drawings. The description of the same configuration as the first embodiment will be omitted. The coil structure and magnetic device according to this embodiment include an insulating layer formed using the resin film 100 according to this embodiment described above. That is, the magnetic device 400 according to this embodiment includes a multilayer wiring board 300A and a core 5, as shown in Figures 7 and 8. A coil-shaped wiring pattern 41 is formed on the multilayer wiring board 300A. Therefore, the multilayer wiring board 300A is a coil structure according to this embodiment. The multilayer wiring board 300A has a hole in the center, into which the core 5 is inserted. Known materials can be used as the core 5, and magnetic materials such as ferrite, compacted magnetic cores, and laminated steel plates can be used.

[0075] [Modifications of Embodiments] The present invention is not limited to the embodiments described above, and modifications or improvements that can achieve the objectives of the present invention are included in the present invention. For example, in the embodiments described above, the multilayer wiring boards 300, 300A, and 300B are wiring boards with a 2-layer to 4-layer structure having 2 to 4 layers of wiring 41, but the invention is not limited thereto. For example, the multilayer wiring board may be a wiring board with a layer structure having 5 or more layers.

[0076] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited in any way by these examples.

[0077] [Preparation Example 1] A 1 L four-neck separable flask equipped with a stirrer, reflux condenser, and thermometer was charged with 0.5 parts by mass of 4,4'-oxydianiline, 4 parts by mass of dimeramine (Croda Japan, PRIAMINE 1075), 6.2 parts by mass of 2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl-bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylate) (TMPBP-TME), and 32 parts by mass of N-methyl-2-pyrrolidone. The mixture was heated and stirred at 50°C for about 3.5 hours while blowing nitrogen into the reaction vessel at a rate of 0.1 mL / sec. After confirming the dissolution of the salt, the mixture was stirred at room temperature for 24 hours to synthesize polyamic acid, a precursor of polyimide. A varnish containing this polyamic acid was then prepared.

[0078] [Preparation Example 2] 98 parts by mass of bisphenol A type epoxy resin "Epiclon 850-S" (manufactured by DIC Corporation, epoxy equivalent: 188), 147 parts by mass of dicyclopentadiene type epoxy resin "HP-7200H" (manufactured by DIC Corporation, epoxy equivalent: 283, softening point: 83°C), 126 parts by mass of aromatic amine-based curing agent "Elasmer 250P" (polytetramethylene oxide-di-p-aminobenzoate, manufactured by Ihara Chemical Co., Ltd.) A mixture consisting of 100 parts by mass of soluble polyimide resin "Q-VR-X0163" (manufactured by PI Technical Research Institute, Tg: 246°C, resin solids content: 20% by mass), 303 parts by mass of phenoxy resin "ERF-001M30" (manufactured by Nippon Steel Chemical & Material, Tg: 146°C, resin solids content: 30% by mass), and 18 parts by mass of flame retardant HCA was prepared to create a resin varnish with a resin solids content of 40% by mass.

[0079] [Preparation Example 1] The varnish containing polyamic acid obtained in Preparation Example 1 was applied to a release film (PET film with mold release treatment), pre-baked at 120°C for 10 minutes to reach the B-stage state, peeled off the release film, placed on a Teflon® plate, and subjected to a heat-curing treatment at 150°C for 60 minutes, followed by a further heat-curing treatment at 180°C for 30 minutes, which caused the polyamic acid to undergo ring-closing polymerization, resulting in an imide-based core film (thickness: 12.5 μm).

[0080] [Preparation Example 2] The resin varnish obtained in Preparation Example 2 was applied to a release film (PET film with mold release treatment), pre-baked at 120°C for 10 minutes to reach the B-stage state, peeled off the release film, placed on a Teflon® plate, and subjected to a heat-curing treatment at 150°C for 60 minutes, followed by a further heat-curing treatment at 180°C for 30 minutes to obtain an epoxy core film (thickness: 12.5 μm).

[0081] [Example 1] A varnish containing polyamic acid obtained in Preparation Example 1 was applied to a copper foil with a thickness of 18 μm, and pre-baked at 120°C for 10 minutes to reach the B stage to produce a copper foil with an adhesive resin layer. The thickness of the adhesive resin layer was 25 μm. Two of these copper foils with adhesive resin layers were placed with the adhesive resin layers facing each other, and the imide-based core film obtained in Preparation Example 1 was sandwiched between them. After lamination, a heat-curing treatment was performed at 150°C for 60 minutes, and then a further heat-curing treatment was performed at 180°C for 30 minutes, thereby ring-closing polymerization of the polyamic acid and the formation of an imide-based cured resin layer, resulting in a double-sided copper-clad laminate substrate.

[0082] [Example 2] A double-sided copper-clad laminate substrate with an epoxy-cured resin layer was obtained in the same manner as in Example 1, except that the resin varnish obtained in Preparation Example 2 was used instead of the polyamic acid-containing varnish obtained in Preparation Example 1.

[0083] [Example 3] A copper foil with a thickness of 18 μm was coated with a varnish containing polyamic acid obtained in Preparation Example 1, pre-baked at 120°C for 10 minutes to reach the B-stage state, and a copper foil with an adhesive resin layer was prepared. Similarly, a PET film with an adhesive resin layer was prepared by coating a release film (PET film with release treatment) with a varnish containing polyamic acid obtained in Preparation Example 1, pre-baking at 120°C for 10 minutes to reach the B-stage state, and a PET film with an adhesive resin layer was prepared. The thickness of the adhesive resin layer in each case was 25 μm. The copper foil with the adhesive resin layer and the PET film with the adhesive resin layer were placed with the adhesive resin layers facing each other, and the imide-based core film obtained in Preparation Example 1 was sandwiched between them and laminated to obtain a resin-coated copper foil. This resin-coated copper foil can be used to fabricate a multilayer wiring board.

[0084] [Example 4] A varnish containing polyamic acid obtained in Preparation Example 1 was applied to the copper foil of a release film (PET film with mold release treatment), and pre-baked at 120°C for 10 minutes to reach the B stage to produce a PET film with an adhesive resin layer. The thickness of the adhesive resin layer was 25 μm. Two of these PET films with adhesive resin layers were placed with the adhesive resin layers facing each other, and the imide-based core film obtained in Preparation Example 1 was sandwiched between them. Lamination was performed to obtain a resin film. A multilayer wiring board can be produced using this resin film.

[0085] [Comparative Example 1] A double-sided copper-clad laminate substrate with an epoxy-cured resin layer was obtained in the same manner as in Example 2, except that the epoxy-based core film obtained in Example 2 was used instead of the imide-based core film obtained in Example 1.

[0086] [Comparative Example 2] A double-sided copper-clad laminate substrate with an epoxy-cured resin layer was obtained in the same manner as in Example 2, except that a commercially available polyimide film (manufactured by Toray DuPont, Kapton®, thickness: 12.5 μm) was used instead of the imide-based core film obtained in Example 1.

[0087] [Comparative Example 3] Two electrolytic copper foils (thickness: 25 μm) were prepared, and these two electrolytic copper foils were placed facing each other. Then, two prepregs (thickness: 100 μm, "R-1551" manufactured by Panasonic Industries) were prepared, the two prepregs were stacked, sandwiched between the two electrolytic copper foils, and a double-sided copper-clad laminate substrate was fabricated by heat pressing. The heat pressing conditions were as follows: the first stage was at a set temperature of 130°C and a pressure of 1.0 MPa for 30 minutes, and the second stage was at a set temperature of 180°C and a pressure of 2.0 MPa for 90 minutes.

[0088] [Evaluation of Multilayer Wiring Boards] Multilayer wiring boards were evaluated (withstand voltage (dielectric breakdown strength and dielectric breakdown voltage of the insulating material), thickness, and relative permittivity) using the following method. The results obtained are shown in Table 1. The layer configuration of the insulating material in Examples 1 and 2, and Comparative Examples 1 to 3 are also shown in Table 1. (1) Withstand voltage All the copper foil of the double-sided copper-clad laminated substrate that was obtained was etched to obtain a sample of the insulating material. For the core layer, the core film used in the example was used as the sample. For the cured resin layer, the adhesive resin layer used in the example was cured under the same conditions as in the example and used as the sample. For the obtained sample, the voltage was increased by 0.5 kV / sec in the thickness direction of the sample over a predetermined area, and the conductive voltage was measured using the "Ultra-High Voltage Withstand Voltage Tester Model 7472" manufactured by Keisoku Gijutsu Kenkyusho Co., Ltd., and the dielectric breakdown strength and dielectric breakdown voltage were calculated. (2) Thickness All the copper foil of the double-sided copper-clad laminated substrate that was obtained was etched to obtain a sample. The thickness of this sample was measured with calipers. (3) Relative permittivity All of the copper foil of the obtained double-sided copper-clad laminated substrate was etched, and then processed into a sample measuring 20 mm x 20 mm with a thickness of 200 μm. The relative permittivity of the obtained sample at 1 MHz was measured using a measuring device ("RF Impedance / Material Analyzer, 1.8 GHz 4291B" manufactured by KEYSIGHT).

[0089]

[0090] As is clear from the results shown in Table 1, the multilayer wiring boards according to the present invention (Examples 1 and 2) were confirmed to have good dielectric strength, thickness, and dielectric constant. In contrast, the multilayer wiring board using two prepregs (Comparative Example 3) had a dielectric breakdown voltage of 20 kV, which was lower than the target of 21 kV, and the insulating material was thicker and had a higher dielectric constant. Furthermore, the multilayer wiring boards obtained in Comparative Examples 1 and 2 had high dielectric constants. Therefore, it was confirmed that the resin film according to the present invention has a low dielectric constant.

[0091] 1...Adhesive resin layer 1a...Curing resin layer 1b...Coated film 2...Core layer 3...Release film layer 4...Copper foil 41...Wiring 5...Core 100...Resin film 200...Copper foil with resin 300, 300A, 300B...Multilayer wiring board 400...Magnetic device

Claims

1. A resin film comprising a core layer and adhesive resin layers provided on both sides of the core layer, wherein the adhesive resin layer is made of a first adhesive resin composition containing polyamic acid which is a polyaddition reaction product of (A) an acid dianhydride and (B) a diamine, or a second adhesive resin composition containing an epoxy resin, wherein the polyamic acid in the first adhesive resin composition contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine components, the dielectric breakdown strength of the cured product of the second adhesive resin composition is 300 kV / mm or more, and the core layer is made of a polyimide film containing a polyimide obtained by imidizing the polyamic acid in the first adhesive resin composition.

2. A resin film according to claim 1, wherein the (A) acid dianhydride has a structure represented by the following formula (1). (In formula (1), Ar represents a substituted or unsubstituted arylene group.) 3. A resin film according to claim 1 or claim 2, wherein the (B) diamine comprises (B2) aromatic diamine.

4. A resin film according to claim 1 or claim 2, wherein the ratio of the thickness of the adhesive resin layer to the thickness of the core layer is 1 / 2 or more and 4 or less.

5. A resin-coated copper foil comprising a resin film according to claim 1 or claim 2 and a copper foil laminated on the resin film.

6. A multilayer wiring board comprising an insulating layer formed using the resin film described in claim 1 or claim 2.

7. A coil structure comprising an insulating layer formed using the resin film described in claim 1 or claim 2.

8. A magnetic device comprising an insulating layer formed using the resin film described in claim 1 or claim 2.

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